the objectives of this study were to compare (a) the effects of trehalose incorporated to ethylene glycol and (b) the effect of ethylene glycol and glycerol associated to trehalose on the viability of frozen swine embryos. treatment 1 consisted in 1.5 m ethylene glycol, treatment 2 in 1.5 m ethylene glycol plus 0.25 m trehalose and treatment 3 glycerol 1.5 m with 0.25 m trehalose. the embryos were frozen at expanded blastocyst stage. the rapid freezing method was used, with a cooling rate of 1°c/minute from the room temperature (± 25°c) to seeding (-7°c), and of 0.3°c/minute to -35°c, when the straws were plunged into liquid nitrogen (-196°c). thawing was carried out in air during 30 seconds and in a water bath at 37°c during 30 seconds. cryoprotectors were removed by the step-wise method. embryo viability was observed microscopicaly imediately after thawing and when they reexpanded after being cultured for 18-24h in medium 199 with 20% bovine foetal serum in 60 ml drops covered with mineral oil and incubated at 37°c in air with 6% co2. the viability was 17.2%, 37.5% and 42.8% immediately after thawing, and 6.9%, 28.1% e 28.5% after a culture period of 18-24h, for treatments 1, 2 and 3, respectively. the results showed no differences (p>0.05) in viability among treatments when observation was made immediately after thawing. after culturing, viability rate was higher (p<0.05) in ethylene glycol with 0.25 m trehalose than in ethylene glycol only. ethylene glycol and glycerol associated to trehalose showed no differences to cryoprotect swine embryos.